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<br />O:la75 <br /> <br />SUMMARY AND CONCLUSIONS <br /> <br />Summary <br />The headwaters of the Arkansas River originate above Leadville <br />at elevations in excess of 12,000 feet. The river flows in a general <br />southeasterly direction through mountainous areas to Canon City where <br />the terrain abruptly changes into the plains. From Canon City, the <br />river flows in a general easterly direction to the state line, about <br />four miles east of Holly. Irrigation in the Arkansas River basin began <br />in the early 1860's by small individual enterprises. This was followed by <br />larger developments and by the early 1900's all of the surface flows had <br />been appropriated for direct use and/or storage, except for major floods <br />generally originating in the plains tributaries from high intensity rain- <br />storms. These flood flows, although of large magnitude at times, do not <br />provide a dependable water supply. <br />Host of the dependable runoff originates from snow in the high <br />mountains above Canon City; consequently, most of the irrigation is <br />along the main stream. Because of the scant snowfall in the upper reaches <br />of the major tributaries below Canon City, irrigation in these basins <br />is quite limited and has little effect upon the flows in the Arkansas <br />River proper. Runoff from snowmelt diminishes rapidly after June, and <br />the lands under a majority of the canals suffer moderate to severe shortages <br />thereafter, especially in average and low runoff years. The variability of <br />flows at Canon City is apparent from the following data: (I) The average <br />annual flow for the 1924-1966 period was 518,000 acre feet; (2) the <br />average monthly flow for June was 126,500 acre feet; (3) for July 83,800 <br />acre feet and, (4) for August was 50,400 acre feet. Contrasted to this, <br />the average full water supply requirements of the canals between Pueblo <br />and the state line are 225,000, 265,000 and 230,000 acre feet, respectively, <br />for these months. <br />Minimum monthly flows at Canon City for the study period fOr June, <br />July and August were 41,200, 24,600 and 18,000 acre feet, and maximum flows <br />for these months were 236,700, 340,800 and 128,000 acre feet, respectively. <br />